This invention relates to a magnetic brake system capable of detecting a trouble of a magnetic brake controlled by an electric current fed through a coil, and also to an elevator trouble detection system using the above magnetic brake system as an elevator drive motor.
As a brake for an elevator, a magnetic brake is generally used. This magnetic brake is constructed such that feeding of an electric current through a coil attracts an armature to separate a lining from a disc for permitting running of a car and cut-off of the electric current causes the armature to return to bring the lining into contact with the disc for applying braking force.
A magnetic brake of such a construction may be locked for various reasons so that the above-mentioned attraction of an armature may be troubled. As occurrence of such a trouble leads to a loss of normal braking force, a serious accident may take place. It is, therefore, required to detect a trouble of a magnetic brake without failure.
As disclosed in JP-A-11222371, for example, it has conventionally been proposed to measure the temperature of the lining by a temperature sensor and, when the measurement value is higher than a criterion, to determine that the gap between the lining and the disc is not normal and abnormal frictional heat is being produced, and to transmit trouble information to a supervision center by which an elevator is supervised at a remote location.
In the above-mentioned conventional art, the determination of a trouble in the magnetic brake is performed based on a comparison between the temperature measured by the temperature sensor and the criterion. However, the air temperature of a location at which an elevator is installed varies depending upon the geographical location or the season, so that measurement values obtained by the temperature sensor also deviate due to variations in air temperature. For accurate detection of a trouble, it is, therefore, necessary to adjust the criterion depending upon the geographical location or the season. However, irksome labor is required for resetting the criterion. Further, a magnetic brake is structurally arranged adjacent an elevator drive motor. Heat produced by the motor is hence transferred to the magnetic brake, leading to a rise in the temperature of the magnetic brake. Depending upon the installation site of an elevator, however, the operation rate of the elevator varies and the quantity of heat produced by its motor also differs. It is, therefore, also necessary to take into consideration the heat to be transferred from the motor upon setting the above-described criterion.
With the foregoing circumstances of the conventional art in view, the present invention has as primary objects thereof the provision of a magnetic brake system capable of detecting a trouble with accuracy and an elevator trouble detection system making use of the magnetic brake system.
To achieve these objects, the present invention, in a first aspect thereof, provides a magnetic brake system for performing braking action by cancellation of energization of a coil, said magnetic brake system comprising a magnetic brake provided with a disc connected to a shaft of a motor and also with an armature responsive to energization of the coil for being attracted to separate the disc from a lining, wherein the magnetic brake system comprises: a temperature detection means for detecting a temperature of the magnetic brake; a temperature comparison means for comparing a first temperature, which is detected by the temperature detection means when the coil is energized to release the magnetic brake, specifically, shortly after the coil is energized to release the magnetic brake, with a second temperature which is detected by the temperature detection means shortly when the energization of the coil is cancelled, specifically, shortly before the energization of the coil is cancelled to actuate the magnetic brake; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a second aspect thereof, provides a magnetic brake system for performing braking action by, said magnetic brake system comprising a magnetic brake provided with a disc connected to a shaft of a motor and also with an armature responsive to energization of the coil for being attracted to separate the disc from a lining, wherein the magnetic brake system comprises: a temperature detection means for detecting a temperature of the magnetic brake; a temperature comparison means for comparing a first temperature, which is detected by the temperature detection means shortly before the energization of the coil is cancelled to actuate the magnetic brake, with a second temperature which is detected by the temperature detection means after a predetermined time is elapsed in continuous actuation of the magnetic brake over the predetermined time since the actuation of the magnetic brake; and a control means for determining on a basis of results of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a third aspect thereof, provides a magnetic brake system for performing braking action by cancellation of energization of a coil, said magnetic brake system comprising a magnetic brake provided with a disc connected to a shaft of a motor and also with an armature responsive to energization of the coil for being attracted to separate the disc from a lining, wherein the magnetic brake system comprises: a first temperature detection means for detecting a temperature of the magnetic brake; a second temperature detection means for detecting an air temperature of an environment in which the magnetic brake is installed; a temperature comparison means for comparing a first temperature, which is detected by the first temperature detection means, with a second temperature detected by the second temperature detection means; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a fourth aspect thereof, provides a magnetic brake system as described above in connection with the first or third aspect, wherein, when a temperature difference between the first temperature and the second temperature as determined by the temperature comparison means is greater than a predetermined value, the control means determines that the magnetic brake has developed a trouble.
The present invention, in a fifth aspect thereof, provides a magnetic brake system as described above in connection with any one of the first to fourth aspects, further comprising an informing means for informing that the magnetic brake has developed the trouble, wherein, when the magnetic brake is determined to have developed the trouble, the control means informs accordingly by the informing means.
The present invention, in a sixth aspect thereof, provides an elevator trouble detection system for detecting a trouble of a magnetic brake for a drive motor of an elevator, said magnetic brake being provided with an armature attractable by energization of a coil in response to a brake release command to separate a lining from a disc for permitting running of a car and returnable by cancellation of the energization in response to a brake actuation command to bring the lining into contact with the disc for applying braking force, wherein the elevator trouble detection system comprises: a temperature detection means for detecting a temperature of the magnetic brake; a temperature comparison means for comparing a first temperature, which is detected by the temperature detection means when the armature has been attracted responsive to the brake release command, with a second temperature which is detected before the armature returns responsive to the brake actuation command; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a seventh aspect thereof, provides an elevator trouble detection system for detecting a trouble of a similar magnetic brake as described above in the preamble of the sixth aspect, wherein the elevator trouble detection system comprises: a temperature detection means for detecting a temperature of the magnetic brake; a temperature comparison means for comparing a first temperature, which is detected by the temperature detection means before the armature returns responsive to the brake actuation command, with a second temperature which is detected by the temperature detection means after a predetermined time is elapsed when braking force is continuously applied for the predetermined time since the return of the armature in response to the brake actuation command; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in an eighth aspect thereof, provides an elevator trouble detection system for detecting a trouble of a similar magnetic brake as described above in the preamble of the sixth aspect, wherein the elevator trouble detection system comprises: a first temperature detection means for detecting a temperature of the magnetic brake; a second temperature detection means for detecting an air temperature of a location at which the elevator is installed; a temperature comparison means for comparing a first temperature, which is detected by the first temperature detection means, with a second temperature detected by the second temperature detection means; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a ninth aspect thereof, provides an elevator trouble detection system for detecting a trouble of a similar magnetic brake as described above in the preamble of the sixth aspect, wherein the elevator trouble detection system comprises: a temperature detection means attached to one of components of the magnetic brake for detecting temperatures of the magnetic brake at predetermined intervals during a period of at least one day; a memory means for storing temperatures detected by the temperature detection means; and a control means for determining that, when a temperature rise from a lowest temperature as detected by the temperature detection means has exceeded a predetermined value, the magnetic brake has developed a trouble.
The present invention, in a tenth aspect thereof, provides an elevator trouble detection system as described above in connection with the ninth aspect, wherein the control means calculates an average daily temperature rise from a difference between a highest temperature and a lowest temperature stored in the memory means during a predetermined period of time, and sets the average daily temperature rise as the predetermined value.
The present invention, in an eleventh aspect thereof, provides an elevator trouble detection system for detecting a trouble of a similar magnetic brake as described above in the preamble of the sixth aspect, wherein the elevator trouble detection system comprises: a temperature detection means for measuring a temperature of the magnetic brake; a temperature comparison means for forcedly operating the elevator continuously for a predetermined time and comparing a first temperature, which is measured by the temperature detection means before initiation of the operation, with a second temperature which is measured by the temperature detection means after the operation; and a control means for determining on a basis of a result of the comparison by the temperature comparison means whether or not the magnetic brake has developed any trouble.
The present invention, in a twelfth aspect thereof, provides an elevator trouble detection system as described above in connection with the sixth, eighth or eleventh aspect, wherein, when a temperature difference between the first and second temperatures as determined by the comparison means is greater than a predetermined value, the control means determines that the magnetic brake has developed a trouble.
The present invention, in a thirteenth aspect thereof, provides an elevator trouble detection system as described above in connection with any one of the sixth to twelfth aspects, further comprising a communication means for making a communication to a supervision center, wherein, when the magnetic brake is determined to have developed a trouble, the control means transmits trouble information to the supervision center via the communication means.
In the first aspect, the temperature detection means arranged, for example, on the magnetic brake measures a first temperature shortly after the coil is energized to attract the armature, and also a second temperature when the energization of the coil is cancelled, in other words, shortly before an armature returns. The temperature comparison means compares the first temperature with the second temperature, and on the basis of a result of this comparison, determines whether or not the magnetic brake has developed any trouble. Described specifically, the temperature comparison means performs a comparison between the temperatures of the magnetic brake at two timings before and after the magnetic brake is actuated and the lining is not in contact with the disc when the magnetic brake is in order. If the magnetic brake is locked, the temperature of the magnetic brake becomes higher due to frictional heat, thereby permitting easy detection of the trouble.
As the air temperature of the location at which the magnetic brake is installed equally affects the measurement of the first temperature and the measurement of the second temperature, any effect of the air temperature itself on the determination can be ignored. Accordingly, a trouble of the magnetic brake can be detected with high accuracy. As a magnetic brake is often used as a brake for a power system in general, the air temperature may be considered to affect the determination of existence or non-existence of a trouble. Any effect of the air temperature itself on the determination can, however, be ignored because the air temperature of the location at which the elevator is installed equally affects the measurement of the first temperature and that of the second temperature.
In the second aspect, the temperature detection means arranged, for example, on the magnetic brake measures a first temperature shortly before energization of the coil is cancelled to actuate the magnetic brake and also a second temperature after a predetermined time is elapsed in continuous actuation of the magnetic brake for the predetermined time since the actuation of the magnetic brake. The temperature comparison means compares the first temperature with the second temperature, and on the basis of a result of the comparison, determines whether or not the magnetic brake has developed any trouble. If the magnetic brake is locked, a temperature arisen due to frictional heat becomes lower after an elapse of the predetermined time, thereby permitting accurate detection of the trouble.
In the third aspect, the air temperature is detected by the second temperature detection means, whereas the temperature of the magnetic brake is detected by the first temperature detection means. The temperature comparison means compares these temperatures with each other, and on the basis of a result of the comparison, the control means determines whether or not the magnetic brake has developed any trouble. As the control means makes the determination on the basis of a result of arithmetic on the measurement value of the first temperature detection means and the measurement value of the second temperature detection means, it is possible to cope with variations in the air temperature and to detect a trouble of the magnetic brake with high accuracy.
In the fourth aspect, the control means determines that the magnetic brake has developed a trouble, when as a result of the comparison by the temperature comparison means, the temperature difference between the first temperature and the second temperature is found to be greater than the predetermined value. As this trouble of the magnetic brake usually takes place as a result of occurrence of locking between the lining and the disc, the magnetic brake is determined to be locked when the temperature difference is greater than the predetermined value.
In the fifth aspect, when the magnetic brake is determined by the control means to have developed a trouble, the informing means informs accordingly. The occurrence of the trouble in the magnetic brake can, therefore, be promptly brought to the supervisor""s attention, thereby permitting a prompt countermeasure to the trouble of the magnetic brake.
In the sixth aspect, a first temperature is measured when the armature has been attracted responsive to a brake release command, and a second temperature is measured before the armature returns responsive to a brake actuation command. Then, the first temperature and the second temperatures are compared with each other by the temperature comparison means, and on the basis of a result of the comparison, it is determined by the control means whether or not the magnetic brake has developed any trouble. This determination is performed as in the twelfth aspect. When a value obtained as a result of the comparison is not greater than a predetermined value, in other words, when no locking exists between the lining and the disc and no temperature rise has taken place, the magnetic brake is determined to be in order. If the value obtained as the result of the comparison is greater than the predetermined value, on the other hand, the magnetic brake is determined to be locked. As appreciated from the foregoing, the detection of locking is effected by a comparison between the first temperature and the second temperature. As the air temperature of the location at which the elevator is installed equally affects the measurement of the first temperature and that of the second temperature, any effect of the air temperature itself on the determination can be ignored. Accordingly, a trouble of the magnetic brake can be detected with high accuracy.
In the seventh aspect, a first temperature is measured before the armature returns responsive to the brake actuation command, and further, a second temperature is measured after a predetermined time is elapsed when braking force is continuously applied for the predetermined time since the return of the armature in response to the brake actuation command. The temperature comparison means compares the first temperature with the second temperature, and on the basis of a result of the comparison, the control means determines whether or not the magnetic brake has developed any trouble. If the magnetic brake is locked, a temperature arisen due to frictional heat becomes lower after an elapse of a predetermined time, thereby permitting accurate detection of the trouble.
In the eighth aspect, the second temperature detection means measures the air temperature of the location at which the elevator is installed, while the first temperature detection means measures the temperature of the magnetic brake while the car is running. The measurement value of the second temperature detection means and that of the first temperature detection means are then compared with each other by the temperature comparison means, and on the basis of a result of the comparison by the temperature comparison means, the control means determined whether or not the magnetic brake has developed a trouble. This determination is performed as in the twelfth aspect. When a value obtained as a result of the comparison is not greater than a predetermined value, it is determined that the magnetic brake is in order without locking between the lining and the disc. When the value obtained as the result of the comparison is greater than the predetermined value, on the other hand, the magnetic brake is determined to be locked. Because the detection of locking is effected on the basis of a result of arithmetic on a measurement value of a temperature sensor and a measurement value of an air temperature sensor as described above, it is possible to cope with variations in air temperature. Accordingly, a trouble of the magnetic brake can be detected with high accuracy.
In the ninth aspect, temperatures of the magnetic brake are measured by the temperature detection means at predetermined intervals during a period of at least one day. The thus-detected temperatures of the magnetic brake are stored in the memory means. When a temperature rise from the lowest temperature among the temperatures of the magnetic brake so stored has exceeded the predetermined value, the control means determines that operation of the magnetic brake is in a troubled state. A temperature rise of the magnetic brake in a normal state is attributed to the external air temperature and also to the transfer of heat from the elevator drive motor. Since temperature rises from the lowest temperature in a day due to the external air temperature and the transfer of heat from the motor are considered to be substantially constant, these temperatures do not exceed a predetermined criterion. If the magnetic brake is brought into a locked state, however, abnormal frictional heat is produced. A temperature rise from the lowest temperature of the magnetic brake, therefore, exceeds the predetermined criterion. It is, therefore, possible to accurately detect a trouble of the magnetic brake without being affected by the geographical location and season at and in which the external air temperature varies, or by the elevator operation rate that varies depending upon the installation site.
In the tenth aspect, an average daily temperature rise during a predetermined period of time is calculated from the difference between a highest temperature and a lowest temperature of the magnetic brake upon operation of the elevator, and this average daily temperature raise is set as the predetermined criterion. This makes it possible to automatically obtain, during operation of the elevator, a criterion which is in conformity with its specific installation site.
In the eleventh aspect, a first temperature is measured before the elevator is forcedly operated continuously, and a second temperature is measured after the operation of the elevator. The first temperature and the second temperature are compared with each other, and the determination is performed as in the sixth or eighth aspect. As understood from the foregoing, the detection of locking is performed by the comparison between the first temperature and the second temperature. As the measurements of the first and second temperatures are conducted before and after the initiation of the forced continuous operation, respectively, a trouble of the magnetic brake can be accurately detected without being affected by the elevator operation rate which differs depending upon the installation site.
In the twelfth aspect, the determination is performed as in the fourth aspect.
In the thirteenth aspect, the control means transmits trouble information to the supervision center via the communication means when the magnetic brake is determined to have developed a trouble. The occurrence of the trouble in the magnetic brake can be promptly found on the side of a control sensor (the supervision center) of the elevator, thereby permitting a prompt countermeasure to the trouble of the magnetic brake.